YmoA functions as a molecular stress sensor in Yersinia

Pathogenic bacteria sense and respond to environmental fluctuations, a capability essential for establishing successful infections. The YmoA/Hha protein family are conserved transcription regulators in Enterobacteriaceae, playing a critical role in these responses. Specifically, YmoA in Yersinia adjusts the expression of virulence-associated traits upon temperature shift. Still, the molecular mechanisms transducing environmental signals through YmoA remain elusive. Our study employed nuclear magnetic resonance spectroscopy, biological assays and RNA-seq analysis to elucidate these mechanisms. We demonstrated that YmoA underwent structural fluctuations and conformational dynamics in response to temperature and osmolarity changes, correlating with changes in plasmid copy number, bacterial fitness and virulence function. Notably, chemical shift analysis identified key roles of a few specific residues and of the C-terminus region in sensing both temperature and salt-driven switch. These findings demonstrate that YmoA acts as a central stress sensor in Yersinia, fine-tuning virulence gene expression and balancing metabolic trade-offs. A wildtype and a ∆ymoA mutant of Yersinia pseudotuberculosis were used for this experiment. Strains were grown overnight at 26°C and subsequently diluted 1:25 into fresh media and cultured for 5h at 26°C at which point samples were taken. Each conditions was repeated 3 times independently.